1. Field of the Invention
This invention relates to a suspended ceiling construction. In one of its aspects the invention relates to a suspended ceiling construction having a concealed support structure and access tiles removable by sliding locking splines from locking to release position.
2. State of the Prior Art
Suspended ceilings are well known. In most typical suspended ceiling structures, evenly spaced suspension beams or support members are suspended from the ceiling or other structural members of the enclosure, and individual ceiling tiles of a given size are suspended between adjacent support members. The support members may be concealed or visible from a position below the ceiling structure, with the concealed support structures involving more complex structural problems than ceilings with visible supports.
Two of the most common types of suspended ceilings in use today are "T-Bar" and "Z-Bar" type structures. In a T-bar grid structure, the support structure comprises a rectangular grid or matrix of inverted T-shaped members or T-bars suspended from the ceiling. The T-bar structure may be visible or concealed, depending on the ceiling tiles mounted in the grid. A visible T-bar system is called a "conventional grid" system, while a concealed T-bar system is called a "concealed grid" system.
In a conventional grid system, individual ceiling tiles rest on the upper surfaces of the horizontal flanges of the T-bars. In this type of construction, access to the space above the ceiling is provided by lifting the tiles upwardly out of the gridwork.
One problem with this type of system is that the flanges on the T-bars are fully visible from below the ceiling, thus impairing the aesthetic qualties of the ceiling and making it necessary to employ finished metal in the T-bars so that the visible portions will be as unobtrusive as possible.
Another problem with a conventional grid system is that the ceiling tiles must be lifted upwardly to gain access to the space above the suspended ceiling. This upward removal requires extra clearance between the suspended ceiling and any structure or ductwork above the suspended ceiling. Three inches of clearance may be necessary for reasonable access. In cases where this extra clearance is not possible or is omitted through poor installation procedures, it is quite difficult to gain access to the space above the tiles.
In concealed grid T-bar structures, the tiles have a kerf in the outside edges thereof and the tiles are fitted over the edges of the horizontal flanges on the T-bars. The grid members are concealed with this type of system, but the tiles are not removable and must be broken to gain access to the space above ths suspended ceiling.
In a Z-bar type of structure, the support structure for the suspended ceiling is formed of evenly spaced parallel support members called Z-bars, which typically are suspended from C-shaped channel members (typically 11/2 inch channel members) that are spaced evenly across the entire width of a room and run in a perpendicular direction with respect to the Z-bars. The channel members are suspended from the ceiling by suspension wire, and the Z-bars are suspended from the channel members by spring wire clips. The Z-bars are similar in cross-sectional configuration to the T-bars of a concealed grid structure in that the Z-bars have a vertical support member with horizontal flanges extending outwardly from the bottom in an inverted T-shaped member. However, the Z-bars also have a horizontal flange extending outwardly from the top of the vertical support member, thus giving the member a roughly Z-shaped cross section. The flange at the top is designed to engage spring clips that hold the Z-bar to the transverse channel members.
The ceiling tiles conventionally employed in a Z-bar structure are twelve inch square tiles, with each tile having a continuous kerf in the side running around the entire tile. The kerf on the back edge of the tile fits over a flange on a back Z-bar, and the kerf on the front edge of the tile fits over a flange on a Z-bar in front of the tile, with the front Z-bar being fitted into position after a row of tiles has been fitted into engagement with the flange on the back Z-bar. "Breather splines," or thin metal plates, are inserted in the kerfs in side edges of adjacent tiles, in order to close the slots between the tiles and eliminate air flow through the slots.
One of the principal advantages of Z-bar ceilings is that the support structure is completely invisible when the ceiling is installed, and this is a very desirable feature. Accordingly, this type of ceiling has been installed in a high percentage of suspended ceiling installations over the past few years.
One of the principal drawbacks with a Z-bar type of ceiling structure is that, like a concealed grid T-bar ceiling, once the ceiling is installed, the tiles are premanently locked in place, and there is not way to gain access to the space above the ceiling without breaking and destroying a number of tiles. Reassembly of the ceiling structure after access has been provided similarly is a difficult task. Since it is important in many installations that access be provided to the space above the suspended ceiling (e.g., for repair or maintenance of lights, air conditioning, electric wiring or other utilities), the inaccessability of Z-bar ceiling structure is a serious deficiency with this type of system.
In order to overcome the problems of inaccessability of suspended ceilings having a concealed support structure, some attempts have been made to design removable access tiles for existing concealed grid T-bar and Z-bar systems, and other attempts have been made to develop new types of ceilings having access tiles. The problems with the access tiles for ceilings having concealed grids have been that the access tiles have been too complex and have employed expensive and complicated clips for holding the tiles in place. In addition, even with workable access tiles, convenient access to the space above the ceiling is still limited to the space immediately above each access tile, and other tiles still have to be broken away to provide an enlarged access area or access to areas where special access tiles are not located.
One of the principal problems with other types of ceiling structures having access tiles is that they do not employ Z-bar ceiling or T-bar support structures but employ special ceiling supports designed especially for that particular ceiling. Hence, in the vast majority of existing installations, wherein Z-bar or T-bar support structures are already in use, it would be necessary to remove and discard the entire support structure in order to switch over to a new type of ceiling. Other problems with these other types of ceiling structures are that they frequently are difficult to install and remove.
The present invention obviates the foregoing deficiencies in the prior art and provides a simple and inexpensive suspended ceiling construction having concealed support members and simple downwardly removable access tiles that may be suspended from either a Z-bar or a T-bar support structure.